Add shared OAuth flows

crates/aether-oauth/src/core/error.rs

@@ -0,0 +1,38 @@
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum OAuthError {
+    #[error("unsupported oauth provider: {0}")]
+    UnsupportedProvider(String),
+    #[error("invalid oauth request: {0}")]
+    InvalidRequest(String),
+    #[error("oauth state is invalid or expired")]
+    InvalidState,
+    #[error("oauth provider returned HTTP {status_code}: {body_excerpt}")]
+    HttpStatus {
+        status_code: u16,
+        body_excerpt: String,
+    },
+    #[error("oauth provider returned invalid response: {0}")]
+    InvalidResponse(String),
+    #[error("oauth transport failed: {0}")]
+    Transport(String),
+    #[error("oauth storage failed: {0}")]
+    Storage(String),
+    #[error("oauth encryption failed")]
+    EncryptionUnavailable,
+}
+
+impl OAuthError {
+    pub fn invalid_request(detail: impl Into<String>) -> Self {
+        Self::InvalidRequest(detail.into())
+    }
+
+    pub fn invalid_response(detail: impl Into<String>) -> Self {
+        Self::InvalidResponse(detail.into())
+    }
+
+    pub fn transport(detail: impl Into<String>) -> Self {
+        Self::Transport(detail.into())
+    }
+}